1. Field of the Invention
The present invention relates to a one-way rotational transfer mechanism having a rotary input shaft and a rotary output shaft which are coaxially arranged, wherein rotation of the rotary input shaft is transferred to the rotary output shaft when the rotary input shaft is rotated, but rotation of the rotary output shaft is not transferred to the rotary input shaft when the rotary output shaft is rotated.
2. Description of the Related Art
Among conventional one-way rotational transfer mechanisms having a rotary input shaft and a hollow-cylindrical rotary output shaft positioned radially outside the rotary input shaft, wherein the rotary input shaft is driven by motor to transfer rotation of the rotary input shaft to the hollow-cylindrical rotary output shaft, a one-way rotational transfer mechanism which prevents the motor from being rotated by rotation of the rotary output shaft (i.e., prevents the rotary input shaft from being rotated by rotation of the rotary output shaft) when the rotary output shaft is rotated has been disclosed in, e.g., Japanese Unexamined Patent Publication H08-177878 and Japanese Unexamined Patent Publication H11-202181.
In the one-way rotational transfer mechanism disclosed in Japanese patent publication No. Hei-08-177878, the one-way rotational transfer mechanism does not operate smoothly and tends to be susceptible to use conditions if an appropriate viscous matter suitable for use conditions of a product incorporating the one-way rotational transfer mechanism (e.g., the operating temperature of the product) is not selected. Moreover, the structure of the one-way rotational transfer mechanism is complicated because it requires a sealing member for sealing the viscous matter.
In the one-way rotational transfer mechanism disclosed in Japanese patent publication Hei-11-202181, the structure thereof is complicated. Moreover, it is difficult to increase the number of rollers serving as torque transfer members due to the complicated structure of the one-way rotational transfer mechanism, and accordingly, the torque which is transferred from the rotary input shaft to the hollow-cylindrical rotary output shaft when the rotary input shaft is driven to rotate cannot be increased very much.